1. Field of the Invention
The present invention relates to an image display apparatus and method, and specifically relates to a technique that controls the backlight brightness of a transparent display panel.
2. Description of the Related Art
In the related art, there is suggested a liquid crystal display apparatus including a function (backlight local dimming (BLD) function) to individually control the backlight brightness of each segment of a backlight unit installed in the back of a liquid crystal panel (PTL 1: Japanese Patent Application Laid-Open No. 2009-204825 and PTL 2: Japanese Patent Application Laid-Open No. 2011-48198).
The liquid crystal display apparatus described in PTL 1 measures the illumination around a display apparatus, performs backlight local dimming control (turns on the BLD function) in a case where the measured illumination is lower than a preset threshold (for example, 200 to 1000 lx (lux)), and does not perform the backlight local dimming control (turns off the BLD function) in a case where the measured illumination is higher than the preset threshold, such that the luminescence brightness of each segment is uniform.
That is, in a case where the illumination is low, it is possible to improve a local contrast feeling by performing the backlight local dimming control. On the other hand, in a case where the illumination is high, a contrast feeling hardly changes even if the backlight local dimming control is performed. Therefore, the current flowed to each light emitting diode (LED) is made constant, such that the degradation of a luminous flux of the LED does not largely vary.
The display apparatus described in PTL 2 detects the illumination on the surface of a liquid crystal panel by a display/sensor unit associated with each segment of a backlight unit, and illuminates each segment so as to provide backlight brightness corrected by a correction value corresponding to the detected illumination. By this means, in a case where part of the liquid crystal panel is in shadow of an object, it is possible to increase the brightness of the shadow part with small outside light illumination and suppress the reflection of the shadow.